From those links:

> Yeah, I think the most likely eventual "removal" path is actually non-blocking alert(). (confirm() and prompt() cannot be converted to non-blocking though, so they'd have to be fully removed)

Blocking Javascript execution is a fundamental part of the `alert` spec. Replacing it with a different, non-JS-blocking thing that happens to share the same name doesn't mean that `alert` wouldn't be removed as it exists today.

And there's just no way at all to make `prompt`/`confirm` non-blocking, they have to block the main JS thread in order to keep the same API.

That breaks the web by definition. There is no way to implement a non-blocking alert(), confirm(), or prompt() in a way that doesn't break existing code that uses them, and that's a lot of code, a lot of the web.